Turbine blade shroud fastening



April 6, 1943 J. K. MOSSER TURBINE BLADE SHROUD FASTENING Filed Jan. 16,1942 INVENT OR JHMES K. MossER TOR AT NEY Patented Apr. 6, 1943 TURBINEBLADE SHROUD FASTENING James K. Mosser, Springfield, Pa., assignor toWestinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application January 16, 1942, Serial No.426,946

2 Claims.

My invention relates to a row of turbine blades having individualintegral shroud elements disposed circumferentially in end-to-endrelation together with tie bands cooperating with tenons formed on theblades for connecting the latter in groups, and it has for its object toprovide a tie band having inner transverse and shallow grooves overlyingcontiguous edges of shroud elements to avoid contact with suchcontiguous edge corners.

Where turbine blades having individual shroud elements are connected byarcuate shroud bands having openings through which riveted or headedtenons extend, difficulty on account of contiguous edge corners may beexperienced both in manufacture and in operation. Small variations inmanufacture are inevitable with the result that, instead of thecontiguous outer courses of shroud elements being in alignment, onecorner may be offset with respect to the adjacent one, with the resultthat the corner of greater radius will bear tightly against the innerface incident to riveting the band in place, thereby not onlyinterfering with assembly but resulting in a state of initial stress atthe section over the engaged corner. Furthermore, in operation, bladedeflection due to centrifugal and vibratory effects, tends to produceoffsetting of corners; and, in resisting this action a severe localizedstress condition may be set up in the section of a band over the cornerexerting pressure thereon. To avoid overstressing of the bands, Iprovide the inner sides of the latter with shallow grooves bridging thecontiguous end corners of the shroud elements.

This and other objects are effected by the invention as Will be apparentfrom the following description and claims taken in connection with theaccompanying drawing, forming a part of this application, in which:

Fig. 1 is a fragmentary view partly in elevation and partly in sectionshowing the improved turbine blade shroud construction;

Fig. 2 is a sectional view taken along the line II-II of Fig. 1;

Fig. 3 is a detail sectional view drawn to larger scale than Fig. 1; and

Figs. 4 and 5 are detail isometric views of a tie band and the outer endof a turbine blade, respectively.

In the drawing, the row of blades It is carried by the rotor II and hasa shroud construction, at 12.

Each blade includes a root element l3, a blade element 14 and a shroudelement l5. The root and shroud elements I3 and I5 of the row arearranged circumferentially in end-to-end relation and form inner andouter boundaries for the blade passages.

The shroud construction, at I2, is formed by the shroud elements [5, thetie bands l6 and the tenons H, the tie bands and tenons connecting theblades Ill in groups. Each tie band has openings l8 for the tenons andthe latter are provided with riveted or headed portions 19 overlappingthe boundaries of the tenon openings to hold the tie bands in place withrespect to the outer surfaces of the shroud elements.

The tie bands have shallow concave grooves 20 extending widthwise and atthe inner faces thereof to form spaces 2! which bridge the contiguousshroud element corners 22 of each blade group.

Each tie band I6 is made of suitable metallic material of uniformsection which is machined or ground to provide the shallow concavegrooves 20.

Provision of the recesses facilitates manufacture and assembly andassures of operation without overstressing the tie band at any section,particularly at sections immediately over the contiguous corners 22. Ifthere is offsetting of a pair of adjacent outer corners 22 of a group,the tie band may be secured in place without interference. Furthermore,as the bridging recesses 20 provide spaces accommodating offsetting,offsetting due to centrifugal or vibratory effects may occur withoutoverstressing at any tie band section immediately over a corner.

While the invention has been shown in one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modifications without departing from thespirit thereof, and it is desired, therefore, that only such limitationsshall be placed thereupon as are specifically set forth in the appendedclaims.

What is claimed is:

1. In an elastic fluid turbine, a row of blades; shroud elementsintegral with the respective blades and arranged circumferentially inend to-end relation to form a shroud construction; and means forconnecting the blades in groups comprising segmental tie bands each ofwhich overlaps the shroud elements of the blades of the associated groupand means for joining each tie band to the shroud elements overlappedthereby; each tie band being of uniform section and having relativelywide and shallow grooves formed at its inner side, extendingtransversely thereof and bridging contiguous outer corners of the shroudelements.

2. In an elastic fluid turbine, a row of blades; shroud elementsintegral with the respective blades and arranged circumferentially inendto-end relation to form a shroud construction; and means forconnecting the blades in groups comprising tenons integral with andextending outwardly from the respective shroud elements,

segmental tie bands having openings through 10 which the tenons extend,and headed or riveted portions provided by the tenons in overlappingengagement with respect to the tie bands to hold the latter in placewith respect to the shroud elements; each tie band being of uniformsection and having relatively wide and shallow grooves formed at itsinner side, extending transversely thereof and bridging contiguous outercorners of the shroud elements.

JAMES K. MOSSER.

